Friday, October 05, 2007

Beggars can't be choosers: sperm competition   posted by Razib @ 10/05/2007 12:19:00 PM

Here is an "interesting" paper, Changes in Sperm Quality and Numbers in Response to Experimental Manipulation of Male Social Status and Female Attractiveness:
Here we show in the fowl Gallus gallus, where social status determines copulation success, that dominant males produce more sperm than subordinates but that the quality of dominant males' sperm decreases over successive copulations, whereas that of subordinates remains constant. Experimentally manipulating male social status confirmed that ejaculate quality (the number and quality of sperm produced) was a response to the social environment rather than the result of intrinsic differences between dominant and subordinate males. We further show that dominant males responded to variation in female sexual ornamentation, which signals reproductive quality, by adjusting the number and quality of sperm they transferred, whereas subordinate males did not: they transferred ejaculates of similar quality to females with different ornament sizes. These results indicate that trade-offs between traits influencing reproductive success before and after copulation, combined with variation in social dynamics and female quality, may favor the evolution of phenotypically plastic alternative reproductive strategies.

Related: Sperm competition.